+
Vinj
-
R
N
Cstat
Iinj
a
b
ANSI11000009_1_en.vsd
ANSI11000009 V1 EN-US
Figure 226: Effective high-resistance generator grounding via a distribution transformer
Another alternative is shown in figure 227 (High-resistance grounding via a grounded wye-broken
delta transformer). In this case the transformer must withstand the large secondary current
caused by primary ground fault. The resistor typically has to be divided as shown in figure
227 to
limit the voltage to the injection equipment in case of ground fault at the generator terminal. This
voltage is often in the range 400 – 500 V. As the open delta connection gives three times the zero
sequence phase voltage this gives too high voltage at the injection point if the resistance is not
divided as shown in the figure
227 . By dividing the resistor in two parts it shall be ensured that
maximum voltage imposed back on injection equipment is equal to or less than 240V.
1MRK 502 066-UUS B Section 7
Impedance protection
423
Technical manual
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